My penis and balls are always at their biggest and heaviest from late afternoon onwards. Come say 5pm my cock hangs nice and balls are massive. During the day my sack is small and tight and cock lot smaller.

By then the heat of the day is often at its highest and...well, kind of like when you take a warm bath. Heat often brings about low hangers, you know? We're also out of our air-conditioned offices by then and out into the heat of late afternoon.

And, of course, gravity has had its chance to pull for a longer period by then, too. Much like we're taller in the morning before we're brought down by the earth's pull.